Butadiene Rubbers
Properties and Applications
Polybutadiene (Budene, PBD) is the second largest volume elastomer. It accounts for approximately 25 percent of the total global consumption of synthetic rubbers.1 PBD is a very elastic rubber that has good abrasion resistance and low heat buildup which is important for many dynamic applications. Compared to natural rubber, it has less resilience and higher heat buildup but greater wear life and low-temperature flexibility.
The two most important types of polybutadiene rubber (PBD, BR) are high-cis polybutadiene with 95 to 97 percent cis content and low-cis polybutadiene with only approximately 35 percent cis along with 55 percent trans and 10 percent pending vinyl units.2 Both rubbers are produced on a very large scale and have a wide range of properties and uses. Two other types of PBD are high-vinyl polybutadiene and high-trans polybutadiene which have very different properties. Both high-cis and low-cis polybutadiene have a similar low glass transition temperature of approximately -100 +/- 10°C, whereas high-vinyl PBD with approximately 80% vinyl units has a much higher Tg of approx. -23°C.4 High-trans PBD, on the other hand, has very different mechanical and thermal properties. For example trans PBD with 89 to 92 percent trans units is a crystalline plastic and not an elastomer that melts between 80 and 98°C.3
Three types of cis polybutadiene are available: high-cis,
medium-cis, and low-cis. The major use of these rubbers is in tires. Approx. 70 percent of the polymer produced goes into side walls and treads.
PBD rubber is usually combined with other elastomers like natural rubber and SBR for tread applications. Other applications are golf ball cores,
inner tubes of hoses for sandblasting, covers for pneumatic and water hoses, fuel for solid rocket boosters (in combination with oxidizers), and toughened plastics.
About 25 percent of the total polybutadiene volume is used to improve the mechanical properties of plastics, in particular those of high-impact polystyrene (HIPS) and acrylonitrile-butadiene-styrene (ABS).
Vinyl and trans PBD are produced on a much smaller scale
and are used for very few applications. For example, high-vinly PBD is sometimes used in high quality tires to improve rebound resilience5 and
high-trans PBD in the outer lay of golf balls.6